Exemplary embodiments relate generally to a method of operating a nonvolatile memory device, and more particularly to a method of operating a nonvolatile memory device which is capable of reading two planes at the same time.
Electrically programmable and erasable nonvolatile memory devices which do not require refresh function of rewriting data at specific intervals are increasingly in demand.
A nonvolatile memory device typically includes a plane having a number of memory blocks. However, nonvolatile memory devices having a multi-plane structure having a number of planes are increasingly more in use.
Several operations are performed in a nonvolatile memory device such as: a program operation for writing data in a memory cell, a read operation for reading data stored in a memory cell, an erase operation for erasing data stored in a memory cell, and so on.
A multi-level cell (hereinafter referred to as “the MLC”) program method is a program method of storing information of 2 bits or more in one cell. In a single level cell (hereinafter referred to as “the SLC”) program method, two states with different threshold voltages are produced by a program operation. In the MLC program method, however, the above program operation is repeatedly performed to store information of 2 bits or more. In the MLC program operation, a least significant bit (hereinafter referred to as “the LSB”) program operation and a most significant bit (hereinafter referred to as “the MSB”) program operation are performed.
When data is read from two planes at the same time, a read operation is performed on the two planes only when the same program operation has been performed on the two planes. That is, only when the MSB program operation has been performed on the two planes or the LSB program operation has been performed on the two planes, the read operation is performed on the two planes at the same time. After the program operation is performed on the two planes so that they have the same program states, the read operation is then performed on the two planes. This presents many problems one of which, inter alia, is that, if the two planes have different program states, the read operation cannot be performed on the two planes at the same time.